Never seen on the ground in the wild, the grey-shanked douc spends almost all of its time feeding high in the treetops. While traversing the canopy, it moves with a distinctive gait on all four limbs and swings between the branches using its elongated arms (4). It prefers to eat young, tender leaves, which may comprise as much as three quarters of its diet, but it will also eat plant buds, fruits, seeds and flowers (1). As this largely leafy diet is of low nutritional value, the grey-shanked douc’s stomach can hold large volumes, and the stomach contents may weigh as much as a quarter of an adult’s body weight (7). At night, the grey-shanked douc sleeps in carefully selected large trees with a thick canopy (5).
Travelling in groups, the size of which varies with habitat quality, the grey-shanked douc is a very social primate, and will readily play and groom together. Motherhood is a shared duty within the group, giving mothers time to feed, as well as helping to integrate the young into the group. Social bonds within these douc groups are vitally important and communication takes place through a wide variety of vocal and visual signals, as well as through tactile communication in the form of social grooming. Most groups are multi-male and multi-female, with more females than males, and there is a marked dominance hierarchy, with all males dominant over the females. Breeding activity is likely to peak between February and June, when there is an abundance of seasonal fruits, and a single infant is born after an estimated gestation period of around 210 days. Females reach maturity at around five years of age, and probably breed every two years (4).